The present invention relates to a method of controlling a system for processing containers and a device for controlling a system for processing containers. The present invention will be described with reference to a system including a blowing machine or a blowing device for plastic bottles and a filling system downstream thereof for filling the containers. However, it is to be noted that the present invention is also applicable to other systems having other processing units for containers.
Such systems which include a blowing machine for containers and a filling machine downstream thereof for the containers, are known from the prior art. In this connection it is also known from the prior art to couple these two processing units kinematically to one another, which means in this case any change of speed in one machine will automatically effect also a change of speed in the other machine. Such systems are the object of the present invention and will be referred to herein also as a block design system. It is further known to separate the various processing units in such systems kinematically from one another, which means for example to allow different working speeds of the two processing units and also a change to the working speed in one unit, while the working speed of the other unit is maintained.
In order to manage such speed differences, a number of diverse devices is known from the prior art. For example, it is known from FR 2 333 613 to provide a conveyor belt for the containers between the two processing units, which conveyor belt has a variable length and is therefore used as a buffer for the containers. From the U.S. Pat. No. 2,932,376 also an automatic transfer unit is known which is also used for buffering different working speeds of two machines to be connected. From the DE 33 10 248 C2 there is also known a transport and diverting device in a bottle processing system, and in this case, too, the drive units of the two machines to be connected may be separated from each other.
As a result of this separation of drives, however, on the one hand the various processing units will have to be installed at a certain spatial distance from one another, with buffer means for containers inserted in between, in order to avoid that for example a short-term standstill of the machine will have influence on the remaining machines of the system. Apart from that, however, these buffer means between the units will themselves introduce a certain vulnerability to failures, and in the case of a failure of the buffer means, the entire system will have to be stopped. The DE 24 36 591 therefore describes a bottle processing system wherein both machines as well as a transfer device disposed between the two are operated synchronously.
During the operation of the above-described system, however, the problem occurs that under certain conditions individual processing units are preferably to be operated at different working speeds, whereas other processing units in the same system need to be operated essentially at the same working speed at all times. For example, it is required for a blowing machine to be operated always at the same working speed, since the intervals during which for example the containers are guided through an oven are precisely determined. Also, the containers have to be blown after an exactly defined time delay after the heating process.
Other machines, however, need to be operated, at least at times, at different speeds. For example, the problem might occur that a bottle filling machine, in the case of a product change, has to start up at a slow speed to make sure that the product which is initially too warm will not brim over. Also, the last containers or bottles can usually not be filled at the full power or working speed, since the level of the product they are to be filled with, and thus the flow speed of the product, decreases in the storage (ring) vessel.
Since, however, the blowing machine, as mentioned, can not or only with major restrictions control its speed, it would be conceivable to provide two operating protocols for the blow-fill-block, one operating protocol for starting up and idle running the block and a second operating protocol for normal operation. With the first protocol, the block will run at a slower speed in order to counteract any foam formation during filling, the second protocol allows an operational mode at normal speed. However, in this case those two protocols will always have to be kept at the same level for the operation of the block. This means that during certain operator adaptations, which may for example have an effect on the first protocol, the second protocol will always have to be adapted accordingly, since otherwise the desired effect may be diminished or cancelled when changing from protocol 1 to protocol 2. This results in the protocol requiring quite a considerable service effort. This variant, however, may well be useful in the case of applications where for example only medium requirements are posed on the quality of the bottles, which means that the protocol is adapted only relatively seldom, since the second protocol, too, will not have to be adapted frequently.